The present invention relation to a bucket tappet for an internal combustion engine with overhead camshaft, and, more particularly, to a bucket tappet in the form of a hollow cylindrical tappet shank, a baseplate supported on a bead of the shank and a guide bush inside the shank.
A bucket tappet of the above mentioned construction is disclosed in EP-PS 0,030,780. An aluminum material tappet shank has a counter-bore at one end in which a hand metal baseplate, is inserted and held by pressing the circumferential collar on the tappet shank against it. The press fit between the baseplate and the tappet shank does not have, however, a sufficient service life. A further disadvantage of this known bucket tappet resides in the mating of different materials as between the aluminum guide bush, a steel material play-compensating element. As a result of the mating of the different materials, the annular gap provided between the two elements as a precondition of functioning of the bucket tappet increases as the operating temperature of the internal combustion engine increases. When the internal combustion engine is hot due to running, a relatively large quantity of leakage oil escapes to the outside via the annular gap, and thus the oil consumption of the internal combustion engine rises.
The object of the present invention is, therefore, a bucket tappet on which a permanent connection is obtained between the baseplate and the tappet shank.
The foregoing object has been achieved according to the present invention by providing a carrier element made of a steel material on which the baseplate is secured, which element is embedded in the tappet shank.
By virtue of the foregoing features of the present invention, the baseplate can be connected to the tappet shank by a permanent connection, such as, for example, laser welding or soldering. Furthermore, due to the design construction of the carrier element as a flanged bush arranged concentrically in the tappet shank with a flange ring bent of at right angles at one end, optimum anchoring in the aluminum material tappet shank of the steel material carrier element, is achieved. At the same time, the bush portion can be used for accommodating and guiding a play-compensating element, which thus replaces an aluminum guide bush. This has the advantage that the bush portion and the play compensating element guided therein consist of the same material, and it is thereby possible to have a narrow annular gap between the two elements, irrespective of the operating temperature of the internal combustion engine. Due to the narrow gap, only a small quantity of leakage oil can escape to the outside, resulting in a reduced oil consumption of the engine.
A particularly hard support of the baseplate on the tappet shank is obtained by providing the flange ring with a flat bearing surface which is in the same plane as the end face of the tappet shank.
An advantage of the present invention is that a relatively rigid support of the bush portion is obtained in the radial direction relative to the shank wall by either resting the bush portion against the outside of ribs or joined to the rib by casting.
Due to an annular widened portion of the bush portion, an oil collecting space is position in front of the play-compensating element and advantageously ensures a permanent oil supply to the play compensating element during the entire operation.